IEEE section 802.11 defines several different standards for configuring wireless Ethernet networks and devices. For example, 802.11 standards include 802.11, 802.11(a), 802.11(b) and 802.11(g), which are hereby incorporated by reference. According to these standards, wireless Ethernet network devices may be operated in either an infrastructure mode or an ad-hoc mode.
In the infrastructure mode, the wireless network devices or client stations communicate with each other through an access point. In the ad-hoc mode, the wireless network devices (which are typically called mobile stations) communicate directly with each other and do not employ an access point. The term mobile station or client station may not necessarily mean that a wireless network device is actually mobile. For example, a desktop computer that is not mobile may incorporate a wireless network device and operate as a mobile station or client station.
A wireless network that operates in an infrastructure mode includes an access point (AP) and at least one client station that communicates with the AP. For example, the wireless network may operate in an infrastructure mode as defined by IEEE 802.11 and other future standards. Since the client stations are often battery powered, it is important to minimize power consumption to preserve battery life. Therefore, some client stations implement a low power mode and an active mode. During the active mode, the client station transmits and/or receives data. During the low power mode, the client station shuts down components and/or alters operation to conserve power. Usually, the client station is not able to transmit or receive data during the lower power mode.
Wireless network devices may be implemented by a system on chip (SOC) circuit that includes a baseband processor (BBP), a media access control (MAC) device, a host interface, and optionally one or more processors. A host communicates with the wireless network device via the host interface. The SOC circuit may include a radio frequency (RF) transceiver or the RF transceiver may be located externally. The host interface may include a peripheral component interface (PCI), although other types of interfaces may be used. The processor(s) may be Advanced RISC Machine (ARM) processor(s), although other types of processors may be used.
The MAC device controls and selects different operating modes of the BBP and the RF transceiver. During operation, the MAC device instructs the BBP and the RF transceiver to transition to a low power mode to conserve power. The BBP and RF transceivers may include phase-locked loops (PLL), which are calibrated using a reference signal that is supplied by a crystal oscillator (XOSC). The SOC may also include voltage regulators that provide regulated supply voltages to the system.
In an infrastructure mode, the MAC device may instruct the BBP and the RF transceiver to transition to a low power mode when all of the client stations are finished communicating with the AP. Usually, the voltage regulator in the BBP, the XOSC, and PLL devices remain active and consume power during the low power mode.
In some conventional approaches, the operating voltage and/or the clock frequency are reduced during the low power mode while still allowing the system to operate at full capacity. In other conventional approaches, the way that functions are implemented is modified to reduce power consumption. For example, the device may lower a frequency of operation so that calculations take longer to complete.
In another approach, a wireless network device has active and low power modes. A first voltage regulator regulates supply voltage during the active mode. A second voltage regulator dissipates less power than the first voltage regulator and regulates supply voltage during the low power mode. The MAC device selects the first voltage regulator during the active mode and the second voltage regulator during the low power mode. A crystal oscillator outputs a timing signal to the first PLL during the active mode. A first oscillator selectively generates a first clock signal during the low power mode. The first oscillator dissipates less power than the crystal oscillator.
In wireless networks, there are many reasons that make it difficult fo stay in the low power mode for a period of time that is sufficient to significantly reduce average power consumption. For example, a client station in an infrastructure network typically waits for an acknowledgement frame from the access point every time the client station transmits a frame to the access point. This increases the required duration of the active mode for all client stations and also consumes unnecessary power.
In some approaches, before the client station can enter the low power mode, the client station must exchange messages or frames with the access point (hereinafter “a power savings frame exchange”). The power savings frame exchange involves data transmission, which is the activity that consumes the most power. Therefore, the power savings frame exchange, which is used each time that the client stations enter the low power mode, further increases power consumption of the client stations.
Referring to FIG. 1, a console gaming system 10 according to the prior art includes a console 12 and input devices 14. The input devices 14 may comprise any conventional input devices for a console gaming system including handheld controllers, mice, and keyboards. The input devices 14 allow a user to interact with a gaming or video entertainment program that is processed by the console 12. Conventional input devices for console gaming systems include wired interfaces such as universal serial bus (USB) interfaces, universal asynchronous receiver-transmitter (UART) interfaces, or other wired interfaces. The wired interfaces limit the mobility of the input devices 14.
Referring now to FIG. 2, a system-on-chip (SOC) 22 in a conventional input device 14 for a console gaming system includes user interfaces 24 and a console interface 26. The user interfaces 24 include a key scan interface 28, a joystick detect interface 30, and a motor control interface 32. The key scan interface 28 detects when a user presses a button on the input device 14 and transmits button information to the console interface 26. The joystick detect interface 30 detects the position of a joystick on the input device 14 and transmits joystick information to the console interface 26. For example, conventional input devices for console gaming systems include both buttons and analog joysticks.
The motor control interface 32 controls a speed of a motor in the input device 14 and enables and disables the motor. The console interface 26 transmits motor control information from the console 12 to the motor control interface 32. Conventional input devices for console gaming systems include motors that produce vibration effects, which enhances a user's interactive experience. The console interface 26 transmits/receives information to/from the user interfaces 24 and the console 12. As illustrated in FIG. 2, the console interface 26 is typically a wired interface such as a USB or UART interface.
In one configuration, the console interface 26 includes an RF transceiver that provides wireless functionality. In this case, the input devices 14 have dedicated RF transceivers that are connected to typical wired interfaces at the console 12. However, the wireless input devices are battery powered. Input devices with wireless functionality may not include motor control interfaces 32 because motors consume high power, which drains batteries very quickly.